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Exploring probiotics-host interactions

intestinal immune and defence responses to Lactobacillus reuteri in health and disease

Karimi, Shokoufeh (2017). Exploring probiotics-host interactions. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2017:40
ISBN 978-91-576-8853-8
eISBN 978-91-576-8854-5
[Doctoral thesis]

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Lactobacillus reuteri, a ubiquitous inhabitant of the mammalian gastrointestinal (GI) tract has known health-promoting effects and various strains are commercially available as probiotics. Several probiosis mechanisms have been suggested in L. reuteri’s mode of action, but the mediators and factors involved are not well understood. This thesis examined the function of probiotics, particularly L. reuteri, in the GI tract by equipping L. reuteri ATCC PTA 6475 and R2LC with reporter genes (luminescence and fluorescence) and a mutant of strain 6475 was generated by inactivation of chaperon dnaK. Different in vitro and in vivo applications of fluorescent and luminescent strains were evaluated, and it was demonstrated that flow cytometry can be a powerful method for determination of plasmid persistence. Biophotonic imaging (BPI) enabled low doses (~1x10^5) of luminescent bacteria to be monitored in the GI tract and revealed retention of large numbers of bacteria in the stomach up to 3 hours post-gavage. The effect of four strains of L. reuteri (6475, R2LC, DSM 17938, 1563F) was examined in an epithelial infection model using IPEC-J2 cells induced by enterotoxigenic E. coli. By analysing transepithelial electrical resistance (TEER) and leakage of FITC-dextran, it was shown that L. reuteri pre-treatment prevented damage by ETEC to epithelial monolayer integrity. The strains also reduced expression of pro-inflammatory cytokines (TNF-alfa and IL-6) and maintained expression of adherens junction(E-cadherin) and upregulated tight junction (ZO-1) proteins.

To further explore the L. reuteri mode of action, five mutants were evaluated in DSS-induced acute colitis and IPEC-J2 models. It was found that dnaK-, pduC-, cmbA-, amidase- and srtA- may not play major roles in the mechanisms by which 6475 maintains mucosal integrity and counteracts inflammation. However, mutants 6475 pduC- and 6475 cmbA- had a tendency to weaken the protective effect of 6475 in the colitis model.

Studies on the effects of L. reuteri strains on mast cell activation and inflammatory response revealed no inhibition of degranulation mediated by IgE-antigen activation, but down-regulated expression of the pro-inflammatory cytokines IL-6 and IL-13, irrespective of degranulation. Thus pre-treatment with L. reuteri strains can protect against intestinal barrier dysfunction and mucosal inflammation, partly through altering junctional complex proteins, mediators of immunity and mast cells.

Authors/Creators:Karimi, Shokoufeh
Title:Exploring probiotics-host interactions
Subtitle:intestinal immune and defence responses to Lactobacillus reuteri in health and disease
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :31 March 2017
Depositing date:30 March 2017
Number of Pages:80
IKarimi, S*., Ahl, D., Vågesjö, E., Holm, L., Philipson, M., Jonsson, H. & Roos, S. (2016). In vivo and in vitro detection of luminescent and fluorescent Lactobacillus reuteri and application of red fluorescent mCherry for assessing plasmid persistence. PLoS One 11(3): e0151969. II Shok
IIShokoufeh Karimi, Torbjörn Lundh, Hans Jonsson, Stefan Roos. Lactobacillus reuteri strains protect the epithelial barrier integrity of IPECJ2 monolayers from the detrimental effect of enterotoxigenic Escherichia coli (ETEC) (Manuscript)
IIIShokoufeh Karimi, David Ahl, Lena Holm, Mia Phillipson, Hans Jonsson, Stefan Roos. Exploring Lactobacillus reuteri probiosis mechanisms in DSSinduced colitis and in vitro infection models (Manuscript).
Place of Publication:Uppsala
Publisher:Department of Molecular Sciences, Swedish University of Agricultural Sciences
Associated Programs and Other Stakeholders:SLU - Research Areas for the Future > Future Animal Health and Welfare (until Jan 2017)
ISBN for printed version:978-91-576-8853-8
ISBN for electronic version:978-91-576-8854-5
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:Q Food science > Q01 Food science and technology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Immunology (Immunology in the medical area to be 30110)
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Microbiology (Microbiology in the medical area to be 30109)
(A) Swedish standard research categories 2011 > 3 Medical and Health Sciences > 304 Medical Biotechnology > Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Agrovoc terms:lactobacillus, probiotics, cytokines, colitis, mast cells, intestinal diseases, gene expression, mucus, in vitro experimentation, disease resistance
Keywords:Lactobacillus reuteri, probiotics, mucosal barrier, biophotonic imaging, IPEC-J2, tight junction, adherens junction, colitis, mast cells, pro-inflammatory cytokines
Permanent URL:
ID Code:14209
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Department of Molecular Sciences
Deposited By: MSc Shokoufeh Karimi
Deposited On:03 Apr 2017 11:11
Metadata Last Modified:10 Sep 2020 13:41

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